The purpose of this page is to allow you to determine the range at which a possible alien radio transmission, such as from Gliese 581 or SHGb02+14a, can be detected, using your choice of assumptions about frequency, antenna dish size, receiver bandwidth etc. Similarly you can calculate and model ideas for sending signals to, or receiving signals from, places like Gliese 581 or OGLE-2005-BLG-390Lb or HD 189733b or 55 Cancri. The Search for Extra Terrestrial Intelligence SETI involves using sensitive radio telescopes to search. You can help the SETI search at home using your own PC to analyse the recorded signals - which are mostly just random noise.
SETI Signal Range Calculator
http://www.satsig.net/seticalc.htm
Namastè.